The present application relates to a secondary battery, comprising (1) a positive
electrode plate; and (2) an
electrolyte solution; wherein a positive
electrode active material is an active material having a
chemical formula of AxB1-xMeO2 or AxB1-xMPO4 with dications A and B, where Me, M, A, B, and x are as defined in the specification; and the
electrolyte solution comprises an
electrolyte salt of the dications A and B, where A and B are as defined in the positive
electrode active material; as well as a method for preparing a corresponding positive electrode active material, a corresponding battery module, a
battery pack, and an electrical apparatus. The secondary battery of the present application comprises a positive electrode active material comprising the dications A and B and an electrolyte solution of a salt of the same dications, which improves the stability of the positive electrode active material and the negative electrode active material, thereby improving the
cycling stability of the battery.